Why New Cubs Pitching Acquisition David Peterson Has Some Bounce-Back Potential

[Andres Chavez]

Image courtesy of © Michael McLoone-Imagn Images

The Chicago Cubs needed to shore up their rotation, and managed to do so last week with the acquisition of David Peterson. He wasn’t cheap—it cost them Cole Mathis, a former second-round pick—but with Ben Brown, Edward Cabrera, and Jameson Taillon dealing with different injuries and Cade Horton and Justin Steele already out for the year, they required warm bodies.

Peterson is a 30-year-old pending free agent, which means he's no more a long-term solution than are Taillon, Matthew Boyd or Shota Imanaga. The Cubs, however, were willing to give the left-hander a chance, so let’s see what he brings to the table. Peterson struggled on a really disappointing Mets team this year, with a 6.09 ERA in 68 innings. There’s some untapped potential here, though, as he demonstrated in a sturdy first start as a Cub over the weekend. He now has a 5.86 ERA but a 3.91 FIP on the season.

What’s the main takeaway from that ERA-FIP gap? Well, Peterson could be in line for a much-improved ERA in Chicago, in front of a really competent defense that fields talented defensive players such as Nico Hoerner, Alex Bregman, Dansby Swanson, Pete Crow-Armstrong, and Ian Happ on a daily basis. For a few months, the Cubs can enjoy a perfectly average left-hander with potential to be a solid mid-rotation starter, as it happened in 2022 (3.83 ERA) and 2024 (2.90 ERA). Even last year, he racked up 3.1 fWAR, so he might be better than average.

What Peterson is not is consistent. Let’s look at his ERA finishes each year since he became a major leaguer in 2020:

• 2020: 3.44
• 2021: 5.54
• 2022: 3.83
• 2023: 5.03
• 2024: 2.90
• 2025: 4.22

We would be lying if we told you which version of Peterson you will get in Chicago, but if we had to guess, we would say somewhere around his current FIP. That’s not bad at all, considering all the injuries the Cubs have had to deal with. Peterson can throw five pitches, but is mainly a sinker-slider guy. He goes to the former 28.5% of the time, and to the latter 24.6% of the time. A four-seamer (22.9% usage), a curveball (12.8%), and a changeup (11.2%) round out his repertoire.

If you take a look at the lefty’s Statcast profile, he doesn’t really stand out at anything other than his excellent 52.9% ground ball rate (89th percentile) and the impressive extension he generates, whcih comes from being a gargantuan human being.

Having such an extreme groundball pitcher in front of one of the best infield defenses in the league is certainly a good idea for the Cubs. It’s also worth noting that two of his breaking pitches have a solid whiff rate: the curveball, at 35.6%, and the slider, at 32.9%. He had a bad sinker (.396 wOBA) and four-seamer (.426 wOBA) season so far with the Mets, so it will be fascinating to see what kind of adjustments the Cubs help him implement, if any. The .352 BABIP opponents achieved against him during his time with the Mets this year, however, says he might just need better support, rather than better stuff.

The overall package might not be overly enticing for Cubs fans, but Peterson has the potential to be a solid mid-rotation arm, and the Cubs can certainly put him in a position to succeed. It's too early to call it a success after one start, but the vision that led them to acquire him is easy to share.

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